There’s a gradual, but a rising tide of rational, enviro-progressive scientists out there who are committed to solving some of the world’s biggest problems. Many of these problems involve touchy subjects, including ways to reduce poverty while improving or maintaining high standards of living elsewhere, the means for ‘sustainable’ electricity generation, and how to limit the human population’s over-consumption and over-production.

Inevitably, however, many well-intentioned, but grossly misinformed environmentalists (‘enviro-conservatives’?) object to technical solutions based on emotional or ideological grounds alone. As self-professed enviro-progressives (but also scientists who base decisions on evidence, logic and balancing trade-offs as part of our everyday work), we hope to reduce this backlash by providing the data and analyses needed to make the best and most coherent decisions about our future.

On 14 September 2012, Japan’s government announced a nuclear-free policy to phase out its nuclear power generation by 2040. Of course, electricity demand would have to be supplied by both renewable energy and fossil fuels to respond the public unwillingness for nuclear power.

But is this most environmentally sound, safest and economically rational aim? In a new paper we’ve just had published in the peer-reviewed journal Energy Policy, we set out to test Japan’s intentions the best way we know – using empirical data and robust scenario modelling.

Before the March 2011 earthquake and tsunami, Japan produced 25% of its total electricity consumption from nuclear power, 63% from fossil fuels (mostly coal and liquefied natural gas), and 10% from renewables (including hydro). Originally, the Japanese government had planned to increase nuclear power up to 45% of supply, and include new renewables builds, to combine to make major cuts in greenhouse gas emissions by 2030 and meet or exceed their Kyoto targets. However, the original plan could reduce emissions by the energy sector from 1122 Mt CO2e in 2010 to < 720 Mt CO2e by 2030 (< 70% of 1990 emission levels).

After the accident, the National Policy Unit in Japan hinted that the original plan was likely to be scrapped in favour of a new scenario, whereby the nuclear target was to be reduced to somewhere between 0–35% and the renewables target increased to 20–30%. These new plans, obviously, will not be able to meet the original emission reduction targets (Cyranoski, 2012; Normile, 2012). Our paper examines the implications of these different energy mixes.

Why do many people think ‘an anti-nuclear policy’ is environmentally friendly or sustainable?

The reasons are varied, but the perceptions basically emanate from at least one of the following concerns:

Safety issues – health problems and land contamination from released radioactive materials

Environmental – Cutting greenhouse-gases is claimed to be more effective using renewables

These ten criteria covered all possible negative impacts of the energy systems we investigated (nuclear power, fossil fuels, and renewables), and compared them based on Japan’s four newly planned scenario options as well as the current condition (before the accident) (Table 1), using multi-criteria decision-making analysis (MCDMA), which is a transparent and objective methodology for choosing among alternative scenarios.

Table 1. Energy mix scenarios for Japan by 2030

Our results clearly show that the less nuclear power is used, the lower will be the sustainability of the future Japanese energy network, based on MCDMA (Fig. 1). The nuclear-free pathway has more negative impacts than the current condition for some environmental and economic criteria (energy security, levelised cost of electricity, greenhouse gas emissions, land transformation, and freshwater consumption). For the other criteria, the current condition has the most negative values.

Fig. 1. A comparison of each sustainability impact criterion for the four proposed future energy scenarios for Japan, and the current condition, from 0 (no negative impact) to 1 (largest negative impact)

All the details of our analyses are explained in the paper (a PDF of which you can be sent by emailing a request to the corresponding author, Prof. Barry Brook). We also outlined some discussion points relevant to this modelling in an article published on The Conversation. What is the take-home message? – Having the appearance of an environmentally friendly energy policy doesn’t necessarily mean you have one.

Of course, it’s a no-brainer that a higher penetration of renewables is better than a fossil-fuel future, but in countries like Japan and South Korea, there a few realities that make renewables potentially less of the cure-all that they are often purported to be. First, many countries with a high human population density cannot supply 100% of their current electricity (let alone energy) consumption using renewable energy sources. Even if targets could be met, the intermittency of renewable sources restricts their usefulness. In other words, the electricity is not always there when need, so massive facilities for energy storage, like pumped hydro, is essential; this in turn requires substantial land transformation, immense new engineering works in often pristine areas, and financial investment, and of course, emits more greenhouse gases.

Second, there is no perfectly safe system in the world. Even a chair can kill you. For example, there were about 1,500 wind power-related accidents and 4 fatalities from 2007–2011 in the UK (according to RenewableUK). In our paper, we cited evidence from a range of authoritative sources, including the International Energy Agency and World Health Organisation, that nuclear power has a much lower accident and death rate, which includes direct and indirect damage and external costs of fatalities, injuries, and evacuations, compared to any fossil fuel sources, and is as safe or safer than most renewables.

Another concern about nuclear power is radioactivity. It is obvious that more nuclear power will produce more radioactive materials in the form of controlled waste. However, coal power – nuclear’s major competitor in Japan – also releases radioactive waste in the form of uncontrolled pollution –as solid waste and fly ash. Indeed, when we only consider ‘uncontrolled radioactive pollutants’, the nuclear-free pathway releases more radioactive materials than any other scenarios.

Third, and most importantly, an anti-nuclear pathway aims to replace a massive ‘greenhouse-gas free’ energy source (nuclear), with other forms of zero-carbon energy sources (renewables), rather than seeking to reduce or displace dependence on coal, natural gas and oil (almost all of which is imported in Japan).

The primary consequence of a no-nuclear choice is, unfortunately, that we run a major risk of losing the battle against global climate change, because we’ve thrown away our best fighting force. The greenhouse-gas emissions of the nuclear-free scenario can reach up to about 421 kg per megawatt hour. By comparison, in the 35% nuclear-power scenario, it is only 262 kg per megawatt hour despite the higher renewable energy share of the former. This means that a high dependence on renewables will not reduce greenhouse gas emissions in Japan due to physical limits and the lack of large-scale energy storage.

So when you look at the numbers and avoid the temptation to let ideology take over, our paper transparently and objectively demonstrates that Japan’s choice to limit its nuclear power generation is the least sustainable option.

Limiting fossil-fuelled electricity generation is the primary concern here – not preferencing or advocating for any particular non-carbon technology. It’s just that nuclear power is the only option that can achieve it in the foreseeable future. We are not saying that renewable energy doesn’t have a role (of course it does) – but nuclear energy is a key component of that long-term sustainability goal. In fact, replacing nuclear power for other sources will allow the role of fossil fuels to expand rather than reduce.

As conservationists (Brook and Bradshaw have worked for almost two decades on research and models aimed at saving endangered species and protecting global biodiversity), we are dedicated to finding solutions that benefit the Earth’s natural systems. If relying on nuclear fission is the only way we can achieve real climate change mitigation, then we have one clear choice. Climate change is possibly one of the biggest additional pressures biodiversity will face over the coming centuries – if we don’t do anything about it, then our ecosystems – our life support systems – will continue to spiral down the gurgler.

Yes, some people might die if we adopt nuclear power globally, but orders of magnitude more people will if we don’t, and biodiversity will suffer all the more.